Feng Wang

Zhejiang University, Hangzhou, Zhejiang Sheng, China

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Publications (17)43.84 Total impact

  • Source
    The Journal of infection 11/2010; 62(1):107-8. · 4.13 Impact Factor
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    ABSTRACT: Yb3+/Er3+ and Yb3+/Tm3+ co-doped LaF3 nanoparticles with upconversion luminescence properties were prepared via the co-precipitation method, followed by heat treatment at different temperatures in the range of 180°C to 600°C. We investigated the influence of heat treatment temperatures on the size, morphology, and upconversion luminescence intensity of the nanoparticles. Significant increases of the particle size and upconversion luminescence intensity of the nanoparticles were observed with increasing heat treatment temperature. The upconversion mechanism of the LaF3:Yb3+,Er3+ and LaF3:Yb3+,Tm3+ nanoparticles was also discussed.
    Journal of Experimental Nanoscience 12/2007; 2(4):303-311. · 0.88 Impact Factor
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    ABSTRACT: Multicolour colloidal PEI/NaGdF4:Ce3+, Ln(3+) (Ln = Tb, Eu, Sm or Dy) nanocrystals were synthesized using a simple one-pot hydrothermal procedure. The nanocrystals consist of well crystallized hexagonal phase and have an elongated spherical shape, with diameters between 25 and 45 nm. Under single-wavelength excitation at 254 nm in the ultraviolet (UV) region, the nanocrystals doped with different lanthanide ions show intense visible (VIS) emissions of different colours. The characteristic luminescence property of the nanocrystals can be attributed to strong absorption of the UV irradiation by the Ce3+, followed by energy transfer to (via Gd3+ sublattice) and emission from the luminescent centres.
    Nanotechnology 01/2007; 18(2). · 3.84 Impact Factor
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    ABSTRACT: Upconverting materials, which can be efficiently excited by near infrared light and emit strong visible light through a process termed 'upconversion fluorescence', have shown great potential for use in biological labelling and imaging. Some upconverting nanoparticles such as NaYF4 doped with lanthanide ions have been synthesized; however, these nanoparticles are not soluble in water, not biocompatible and do not have functional chemical groups for conjugation of biomolecules, and as a result their bioapplications are very limited unless some surface modifications are performed. Here we report a method for one-pot synthesis of polyethylenimine/NaYF4 nanoparticles doped with lanthanide ions, which are water soluble and biocompatible. The amino groups of polyethylenimine existing on the nanoparticles can be used for attachment of biomolecules. The nanoparticles showed a spherical shape with an average size of about 50 nm. Different lanthanide ions (Yb3+, Er3+ and Tm3+) were doped into the nanoparticles, which showed strong upconversion fluorescence of different colours in aqueous solutions under excitation at 980 nm.
    Nanotechnology 11/2006; 17(23):5786. · 3.84 Impact Factor
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    ABSTRACT: The lanthanide-doped GdF<sub>3</sub> nanoparticles have been produced by a simply hydrothermal synthesis procedure. The excitation and emission spectra of the Eu<sup>3+</sup>-doped GdF<sub>3</sub> nanoparticles showed that the excitation energy of Gd<sup>3+</sup> is efficiently transferred to Eu<sup>3+</sup> in the Eu<sup>3+</sup>-doped GdF<sub>3</sub> nanoparticles. Due to very low phonon energies of GdF <sub>3</sub> matrix, the <sup>5</sup>D<sub>1</sub> emission of Eu<sup>3+ </sup> ions in the Eu<sup>3+</sup>-doped GdF<sub>3</sub> nanoparticles can be observed at room temperature when the doping concentration of Eu <sup>3+</sup> ions is lower than 15 mol%. The luminescence intensity of the Eu<sup>3+</sup>-doped GdF<sub>3</sub> nanoparticles increased with increasing concentration of Eu<sup>3+</sup> ions and reached a maximum at approximately 15 mol%. The Er<sup>3+</sup>-doped GdF<sub>3</sub> nanoparticles exhibit the typical emission spectra of Er<sup>3+</sup> in the near-infrared region. The upconversion emission of the Er<sup>3+ </sup>/Yb<sup>3+</sup> codoped GdF<sub>3</sub> nanoparticles can also be observed. However, the upconversion emission intensity of the Er<sup>3+ </sup>/Yb<sup>3+</sup>-codoped GdF<sub>3</sub> nanoparticles was much weaker than that of the Er<sup>3+</sup>/Yb<sup>3+</sup>-codoped GdF<sub>3</sub> bulk crystal
    IEEE Transactions on Nanotechnology 04/2006; · 1.80 Impact Factor
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    ABSTRACT: Water-soluble lanthanide-doped LaF3 nanocrystals were synthesized using a simple method carried out in aqueous solution at low temperature. The nanocrystals have a nearly spherical shape and an average size of below 30 nm. They consisted of well crystallized hexagonal phases. The luminescence quantum efficiency was about 16% in aqueous solution. LaF3 nanocrystals doped with different lanthanide ions (Eu3+, Ce3+, Tb3+, and Nd3+) were synthesized, which showed strong luminescence in the visible (VIS) and near-infrared (NIR) spectral regions.
    Journal of Materials Chemistry 03/2006; 16(11):1031-1034. · 5.97 Impact Factor
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    ABSTRACT: Lanthanide-based nanocrystals have shown great potential to be used as luminescent materials but their biological applications have been limited because most of the nanocrystals synthesized so far are not water soluble or biocompatible. We report a very straightforward method to synthesize water soluble and biocompatible LaF3 nanocrystals doped with Eu3+ via facile co-precipitation with a natural biopolymer, chitosan. The nanocrystals are very fluorescent and have a small size of about 20 nm. Chitosan is found to cap the nanocrystals during the synthesis process, which renders them water soluble and biocompatible, and provides functional groups such as hydroxyl and amino groups for further attachment of biomolecules. The nanocrystals remain stable in aqueous solution with pH ranging from 2 to 7.4. The nanocrystals are very suitable for use in biological applications, for example, intracellular labelling or measurements, because they are very small in size.
    Nanotechnology 02/2006; 17(5):1527. · 3.84 Impact Factor
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    ABSTRACT: The use of labelling or staining agents has greatly assisted the study of complex biological interactions in the field of biology. In particular, fluorescent labelling of biomolecules has been demonstrated as an indispensable tool in many biological studies. Types of fluorescent labelling agents that are commonly used include conventional classes of organic fluorophores such as fluorescein and cyanine dyes, as well as newer types of inorganic nanoparticles such as QDs, and novel fluorescent latex/silica nanobeads. The newer classes of fluorescent labels are gaining increasing popularity in place of their predecessors due to their better optical properties such as possessing an enhanced photostability and a larger Stokes shift over conventional organic fluorophores, for example. This paper gives an overview of the recent advances on these luminescent nanomaterials with emphases on their optical characteristics that are crucial in fluorescence microscopy, both advantages and limitations in their usage as well as challenges they face, and puts forward the future direction of fluorescent labels in the area of biolabelling.
    Nanotechnology 11/2005; 17(1):R1. · 3.84 Impact Factor
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    ABSTRACT: Europium-doped LaF3 nanoparticles have been prepared by the ionic reaction in the ethanol at 60 degrees C. From the XRD pattern of nanoparticles and the emission spectra of Eu3+ ions, it has been concluded that the Eu3+ ions could easily substitute the La3+ sites and the solid solution La(1-x)Eu(x)F3 can be synthesized. Due to very low phonon energies of LaF3 matrix, the 5D1 emission of Eu3+ ions in La(1-x)Eu(x)F3 nanoparticles can be observed at room temperature when doping concentration of Eu3+ ions is lower than 30 mol%. The quenching process of 5D1 emission can be attributed to cross-relaxation. Since clusters of Eu3+ ions and resonance energy transfer only occurs within one particle due to the hindrance by the particle boundary, the concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurs at higher Eu3+ concentrations in the Eu3+ doped LaF3 nanoparticles.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 10/2005; 61(11-12):2455-9. · 1.98 Impact Factor
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    ABSTRACT: Luminescent Ca1−xF2+x:Eux nanoparticles were synthesized by a chemical co-precipitation method in an ethanol solution. The Ca1−xF2+x:Eux nanoparticles exhibit a sphere-like morphology with particle diameter of about 15–20 nm. With increasing concentration of Eu3+ ion the intensity of XRD diffraction peaks decreased significantly and full width at half-maximum of the peaks increased gradually, which indicated that more Eu3+ ions resulted in the increase of structural defects. The emission spectrum of Ca1−xF2+x:Eux nanoparticles consisted of a few narrow, sharp lines corresponding to Eu3+ ions. The luminescence intensity of Ca1−xF2+x:Eux nanoparticles increased with increasing concentration of Eu3+ ion and reached a maximum at approximately 15 mol%.
    Solid State Communications 03/2005; · 1.53 Impact Factor
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    ABSTRACT: NaLa(WO4)2 powders doped with Eu3+, Nd3+, and Er3+ have been synthesized by a mild hydrothermal method and a crystal of exclusive scheelite phase could be obtained at low temperature. From the spectrum of Eu3+ it has been concluded that the dopant Eu3+ ion occupies a La3+ site and mainly takes the site with C2 symmetry. The higher quenching concentration can be observed in the Eu3+-doped NaLa(WO4)2 powders. The Er3+- and Nd3+-doped NaLa(WO4)2 powders exhibit luminescence in the near infrared (Er3+ at 1550nm, and Nd3+ at 1060nm). The transition mechanism of the up-conversion luminescence of the Er3+-doped NaLa(WO4)2 powders can be ascribed to two photons absorption process.
    Journal of Solid State Chemistry 01/2005; 178(3):825-830. · 2.04 Impact Factor
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    ABSTRACT: The luminescence behavior of the dibenzoyl methane europium(III) complexes (Eu(DBM)3) in sol–gel derived host materials have been investigated. The steady-state excitation and emission spectra and the time-resolved spectra of the 1% EuCl3 and 3% DBM co-doped gel indicated an efficient ligand-to-metal energy transfer. The Eu(DBM)3 complexes in the gel showed longer 5D0 lifetimes in comparison with Eu(DBM)3·3H2O complexes. The luminescence intensity of the 1% EuCl3 and 3% DBM co-doped gel decreased continuously with increasing temperature and time of heat treatment, which indicated the gradual decomposition of the Eu(DBM)3 complexes in the gel during heat treatment.
    Journal of Luminescence 01/2005; 114(3):281-287. · 2.14 Impact Factor
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    ABSTRACT: The Y1−xBO3:Ndx nanoparticles have been prepared by a mild hydrothermal method and luminescence properties in the NIR of Y1−xBO3:Ndx nanoparticles have been investigated. The Y1−xBO3:Ndx nanoparticles with 0–15mol% Nd3+ were found to be isostructural with YBO3 crystal. The preferential nucleation and growth of Y1−xBO3:Ndx nanoparticles along a certain plane can be observed and the dopants of Nd3+ ions would help to weaken the selectivity of the growth of Y1−xBO3:Ndx nanoparticles. The emission spectrum in the NIR of Y1−xBO3:Ndx nanoparticles consisted of a few narrow, sharp lines corresponding to the 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions of Nd3+ ions when pumped with 800nm laser radiation. The luminescence intensity of Y1−xBO3:Ndx nanoparticles increased remarkably with the increase in the doping concentration of Nd3+ ions and reached a maximum at approximately 10mol%.
    Journal of Solid State Chemistry 01/2004; 177(10):3346-3350. · 2.04 Impact Factor
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    ABSTRACT: The luminescence behavior of the europium (Eu) complexes with hexafluoracetylacetonate (HFA:Eu3+ complexes) in the ORMOSIL matrices has been investigated. The steady-state excitation and emission spectra of the 1 mol.% EuCl3 and the 3 mol.% hexafluoracetylacetonate (HFA) co-doped gel were similar to that of the HFA:Eu3+ complexes powders which were synthesized in ethanol solution, which indicated that the HFA:Eu3+ complexes have been synthesized in the 1 mol.% EuCl3 and the 3 mol.% HFA co-doped gel. The time-resolved spectra of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel exhibited the ligand-to-metal energy transfer process, which also confirmed the synthesis of the HFA:Eu3+ complexes in the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel. The decay curves of the luminescence 5D0 state obtained by monitoring the 5D0→7F2 emission line for the HFA:Eu3+ complexes powders and for the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel could both be fitted to a single-exponential fitting function. The temperature of heat treatment has significant influence on the luminescence behavior of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel. The luminescence intensities of the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gel reached a maximum at approximately 110°C and decreased gradually with increasing temperature. However, the 5D0 excited-state lifetimes of the Eu3+ ions in the 1 mol.% EuCl3 and 3 mol.% HFA co-doped gels increased gradually with increasing temperature.
    Materials Science and Engineering B-advanced Functional Solid-state Materials. 01/2003; 100(2):147-151.
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    ABSTRACT: The in situ synthesis processes and luminescence behaviors of the 2-pyridinecarboxylic acid europium (PA:Eu3+) complexes in sol–gel derived host materials have been investigated. The Raman scattering spectrum of the 1mol% EuCl3 and 3mol% PA co-doped gel was similar to that of the PA:Eu3+ complex powders that were synthesized in ethanol, which indicated that the PA:Eu3+ complexes have been in situ synthesized in the 1mol% EuCl3 and 3mol% PA co-doped gel. The excitation and the emission spectra of the 1mol% EuCl3 and 3mol% PA co-doped gels, which were similar to that of the PA:Eu3+ complex powders, also indicated an efficient ligand-to-metal energy transfer which belonged to the complexes. The decay curve of the 1mol% EuCl3 and 3mol% PA co-doped gel can be fitted to a double-exponential function. After the gel was heated at 90°C for 12h, the decay curve can be fitted to a single-exponential function due to vaporization of the most residual water in the gel. The dependence of luminescence intensity and the decay time of x% EuCl3 and 3x% PA co-doped gels that were heated at 90°C for 12h on various concentrations of the EuCl3 and PA were also investigated. The luminescence intensity and the decay time reached a maximum for 1mol% EuCl3 and 3mol% PA co-doped gel that were heated at 90°C for 12h.
    Materials Chemistry and Physics - MATER CHEM PHYS. 01/2003; 82(1):38-43.
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    ABSTRACT: The in-situ synthesis and photophysical properties of a p-hydroxybenzoic acid–terbium (PHBA–Tb3+) complex in sol–gel derived host materials have been investigated. The Raman scattering spectrum of a 1% TbCl3–3% PHBA co-doped gel was the same as that of the PHBA–Tb3+ complex powders synthesized in ethanolic solution, indicating that the PHBA–Tb3+ complex was synthesized in the 1% TbCl3–3% PHBA co-doped gel. The steady-state excitation and emission spectra of the 1% TbCl3–3% PHBA co-doped gel, which were similar to those of the PHBA–Tb3+ complex powders, also indicated the synthesis of the PHBA–Tb3+ complex in the 1% TbCl3–3% PHBA co-doped gel. The time-resolved spectra of the 1%TbCl3–3% PHBA co-doped gel indicated an efficient ligand-to-metal energy transfer, which also confirmed the synthesis of the PHBA–Tb3+ complex in the gel. The luminescence decay curve of the 1% TbCl3–3% PHBA co-doped gel could be fitted by a double-exponential function. Due to the less efficient non-radiative 5D4 relaxation processes in the gel, the presence of the PHBA–Tb3+ complex in the gel led to greatly increased 5D4 lifetimes.
    Journal of Materials Chemistry 01/2002; 12(12):3560-3564. · 5.97 Impact Factor
  • Yong Zhang, Feng Wang
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    ABSTRACT: Nanoparticles (NPs) are a new class of advanced materials with sizes ranging from 1 nm to 100 nm. They have special physicochemical properties that are very different from those of bulk materials. For example, metal nanoparticles smaller than 5 nm show remarkable quantum size effects, which endow them with peculiar physical and chemical properties. The superlattices of metal nanoparticles exhibit novel electronic and optical properties that are not present in the isolated particles. The sizes of the nanoparticles are close to those of biomolecules, which allows an integration of nanotechnology and biotechnology, leading to major advances in multiplexed bioassays [1–3], clinical therapies [4], ultrasensitive biodetection, and bioimaging [5,6]. Moreover, nanoparticles can be used as building blocks for the fabrication of micro/nanoscale constructs with highly ordered architectures.